Just require URLs

Didier PH Martin martind at netfolder.com
Wed Jun 2 18:06:19 BST 1999


<point of view>
a) because a URI could be used to specify a XML name space, we can use
either URLs and URNs because both are URIs.
b) If we have some forward thinking on the subject, someday, this URI will
points to a "place" containing the name space documentation. The ideal world
is that the documentation contains both human readable and machine
interpretable documents.
c) If we choose to use a URL for a name space identifier, we create location
dependency to our documents, If we choose URNs, the documents are then
location independent. Again, with some forward thinking, the name space
documentation may be moved to a registry or moved to several industry
registry and still be retrievable (in the case of URNs). In the case of name
space documentation referred with a URL, the links become broken if we move
the documentation from one "place" to another. Also a some URL like the HTTP
URLs points to a single location. A URN can point to several locations.
d) like for URL, for human consumption and readability, URN could be written
with "/" without encoding. However, the resolution mechanism will have to
encode these delimiters before URN->URL transformation on a URN resolver
(could be a DNS or any other kind of server like for instance LDAP). This is
what is done with most modern browsers today. The user enters a URL
containing spaces in the text box and each space gets encoded before the URL
gets resolved into a resource on the HTTP server.

URN brings more longevity to information elements contained in the published
document. The URN can be resolved as long as a resolver has been created to
resolve its particular name space (URN name space). In the case of URLs any
documentation movement leads to a break of the links and the document is no
longer linked to its documentation. Thus, in this case, the document has a
shorter longevity (because we cannot retreive the document vocabulary rules
and meanings).

Didier PH Martin
mailto:martind at netfolder.com

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